During the last review period, we have developed a sensitive, reliable and quantitative method which allows simultaneous determination of enantiomeric SAL and its precursor DA in biological samples using simple chemical derivatization and chiral separation coupled with electrospray ionization-tandem mass spectrometry (ESI-MS/MS). During this period, we have investigated the effects of diet and ethanol on SAL levels in humans and rodents using this method. To test the influence of acute ethanol infusion and diet on plasma SAL levels, plasma samples were collected from healthy subjects before and 1h after a standard meal including a banana as well as during a period of ethanol infusion at 0.08%. Plasma SAL levels were increased significantly in response to diet including banana, contributing to the individual variability of the basal SAL level. In contrast to the diet effect, ethanol infusion did not significantly affect the plasma SAL level and its enantiomeric profile. We also examined the effect of diet on the time course of the plasma SAL profile in an animal model. The plasma was obtained from rats fed with SAL (10 g/mL) or banana solutions (3g), and analyzed at different time points (0-24h). We found that the plasma SAL and DA levels were significantly elevated within an hour of feeding SAL or banana, which lasted at least 8 hours. The data suggested that dietary contribution should be given serious consideration when evaluating plasma SAL and DA levels. We have also studied the effect of ethanol on SAL levels in brain regions of alcohol preferring- (P) in comparison to non-preferring (NP) rats. We found that SAL and DA levels are similar in the striatum of NP and P rats, but significantly lower in P rats in the nucleus accumbens. Ethanol exposure significantly decreased both SAL and dopamine levels in the striatum. In NA, only dopamine level decreased with ethanol drinking in P rats. To understand inconsistencies of the results between ours and previously reported increased level of SAL with ethanol treatment, the possible effect of ethanol on the extracellular SAL concentrations in the brain will be evaluated.